COOPERATIVE  IMPROVEMENT  OF  CITRUS  VARIETIES 

By 

A.  D.  Shamel 

Separate  No.  813,  from  Yearbook  of  the 
U.S.D.A.  1919. 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


;ORTI< 

COLLEGE  OF  AGRICULTURE 
BERKELEY,  CAI IFORNIA 


IMPROVEMENT 
CITRUS 


By  A.  D.  SHAMEL, 

Physiologist  in  Charge  of  Fruit-Im- 
provement Investigations,  Office  of 
Jlorticnltiiral  ami  PomolOffiCttl  Inves- 
tigations Bureau  of  Plant  Industry. 

IMPORTANCE  OF  THE  CALIFORNIA  CITRUS  VARIETIES. 

DURING  the  crop  year  1918-19  about  39,100  carloads  of 
oranges  and  grapefruit  and  9,963  carloads  of  lemons, 
or  49,063  carloads  of  citrus  fruit,  were  shipped  from  Cali- 
fornia. In  the  wholesale  markets  this  crop  brought  more 
than  $100,000,000.  After  the  expenses  incurred  in  packing, 
transporting,  and  marketing  were  deducted  from  this 
amount,  approximately  $75,000,000  was  returned  to  the  cit- 
rus growers  in  California.1 

Only  a  few  varieties  of  cftrus  fruits  were  grown  to  pro- 
duce this  result.  The  Washington  Navel  orange  crop, 
which  ripens  during  the  winter  months,  amounted  to  ap- 
proximately 17,000  carloads;  the  Valencia  orange  crop, 
which  ripens  during  the  summer  months,  amounted  to  about 
20,000  carloads.  Other  orange  varieties  of  minor  impor- 
tance produced  about  1,500  carloads.  The  Eureka  and  Lis- 
bon varieties  of  lemons,  differing  mainly  in  the  season  of 
production,  so  that  mature  fruits  are  marketed  during  the 
entire  year,  produced  9,963  carloads.  The  Marsh  is  the  only 
grapefruit  variety  grown  commercially,  and  this  crop,  which 

1  Information  furnished  by  the  California  Fruit  Growers'  Exchange. 

Separate  No.  813,  from  Yearbook  of  the  Department  of  Agriculture,  1919. 

249 

172146°— 20 1 


Of 


250       Yearbook  of  the  Department  of  Agriculture,  1910. 

ripens  during  the  summer  months,  amounted  to  about  600 
carloads  of  fruit. 

The  high  commercial  reputation  of  the  California  citrus 
fruits  has  largely  resulted  from  marketing  regular  and  uni- 
form supplies  of  good  fruit  .produced  by  a  few  standard 
varieties,  which  are  readily  identified  by  the  trade  and  by 
the  consumers.  For  this  reason  the  importance  to  the  cit- 
rus industry  of  conserving  and  improving  these  varieties, 
now  that  their  reputation  has  become  fully  established,  must 
be  apparent  to  every  thinking  person. 

Most  of  the  development  of  the  citrus  industry  in  Cali- 
fornia to  its  present  great  commercial  importance  has  taken 
place  within  the  last  25  years.  Its  rapid  growth  during  this 
period  is  one  of  the  marvels  of  horticulture.  The  princi- 
pal markets  for  the  crop  are  a  long  distance  from  where 
the  fruit  is  grown.  The  climate,  soil,  and  cultural  condi- 
tions in  the  citrus  districts  necessitate  constant  vigilance 
and  intelligent  effort  in  order  to  produce  successful  crops. 
These  and  other  circumstances  have  resulted  in  the  develop- 
ment of  many  improved  cultural  and  marketing  practices, 
largely  by  the  aid  of  scientific  research,  which  have  proved 
to  be  invaluable  not  only  in  the  profitable  growing  and 
marketing  of  citrus  crops  in  California,  but  also  in  the 
production  and  marketing  of  fruit  crops  in  other  sections 
of  the  United  States. 

OCCURRENCE  AND   FREQUENCY  OF  BUD  VARIATION. 

During  recent  years  many  California  citrus  growers  have 
noticed  the  presence  of  undesirable  trees  in  their  orchards. 
This  condition  seemed  more  apparent  in  young  orchards  or 
those  farther  removed  from  the  original  trees  from  which 
the  varieties  developed  than  in  "the  older  orchards  which  were 
more  closely  related  to  the  original  parent  trees.  .  Many 
of  these  trees  apparently  produced  irregular,  light  crops  of 
inferior  quality.  In  some  cases  the  commercial  and  eating 
quality  of  the  fruit  from  the  offtype  trees  proved  to  be  so 
poor  that  it  became  necessary  to  sort  them  out  from  the 
general  crop  and  throw  them  into  the  cull  bins.  This  con- 
dition increased  the  expense  of  assorting  the  crop  and  also 
materially  reduced  the  merchantable  yield  of  the  orchards. 
In  many  instances  the  inferior  and  worthless  fruits  from 
the  undesirable  trees  could  not  be  easily  identified  in  the 


Cooperative  Improvement  of  Cities  Varieties.      251 

packing  houses  and  were  inadvertently  included  with  the 
regular  pack;  the  consumer  was  disappointed  in  their  eating 
quality,  and  a  loss  of  reputation  for  the  crop  as  a  whole 
inevitably  resulted. 

Acting  upon  the  request  of  some  of  the  leading  citrus 
growers  in  southern  California,  the  Bureau  of  Plant  In- 
dustry in  1909  began  an  investigation  for  the  purpose  (1) 
of  ascertaining  the  variations  which  have  taken  place  in 
the  important  commercial  citrus  varieties  grown  in  Cali- 
fornia through  bud  variations  and  to  learn  the  comparative 
value  of  the  different  strains  arising  from  these  variations 
for  commercial  fruit  production;  (2)  to  determine  the  ex- 
tent to  which  undesirable  variations  have  been  propagated, 
as  shown  by  the  percentage  of  such  undesirable  trees  exist- 
ing in  the  parent  bearing  orchards;  and  (3)  through  im- 
proved methods  of  propagation  to  reduce  the  number  of 
undesirable  variations  which  enter  into  commercial  citrus- 
fruit  orchards. 

These  investigations  have  been  carried  on  by  means  of 
records  and  observations  of  individual  trees.  The  term 
"performance  record"  is  used  here  to  mean  the  record  of 
the  number  and  commercial  quality  of  fruits  borne  by  indi- 
vidual trees  during  a  period  of  years.  Mostly  these  studies 
were  made  in  performance-record  plats,  consisting  of  groups 
of  trees  gr&wn  under  comparable  conditions,  selected  for 
the  purpose  of  determining  the  behavior  of  the  trees  by 
means  of  individual-tree  records  of  production,  observations, 
descriptive  notes,  and  photographs. 

In  addition  to  securing  accurate  individual-tree  yield 
records,  a  very  careful  study  of  the  tree,  flower,  and  fruit 
characteristics  was  made.  These  data  showed  that  striking 
bud  variations  were  of  frequent  occurrence  in  many  of  the 
citrus  trees.  For  example,  typical  Washington  Navel 
orange  trees  each  grown  from  a  single  bud  and  bearing 
fruits  similar  to  those  shown  in  figure  1,  were  often  found 
bearing  several  distinct  types  of  navel  oranges,  such  as  those 
shown  in  figure  2.  In  some  cases  these  variations  occurred 
as  single  fruits  possessing  characteristics  different  from 
those  of  the  Washington  Navel  orange.  In  other  instances 
Washington  Navel  orange  trees  were  discovered  having  one 
large  Ijmb  bearing  many  fruits  which  were  so  different  from 
the  other  fruits  on  the  tree  as  to-be  classed  as  belonging  to 


210105 


252      Yearbook  of  the  Department  of  Agriculture,  1919. 

a  totally  different  variety.  Several  individual  trees  were 
found  on  which  nine  different  strains  of  the  navel  orange 
were  borne  on  different  limbs,  all  of  them  arising  as  bud 
sports  in  these  trees.  The  differences  in  the  characteristics 
of  the  fruit  variations  in  some  of  the  trees  were  found  to  be 
almost  as  important  from  the  commercial  standpoint  as 
those  which  differentiate  horticultural  varieties.  These 


Best  Strain  of  the  Washington  Navel  Orange. 

•FiG.  1. — Typical  fruits  from  a  tree  of  the  best  strain  of  the  Washington  Navel 
orange  variety. 

variations  were  not  confined  to  the  Washington  Xavel 
orange,  but  were  found  almost  as  frequently  in  the  trees  of 
the  other  varieties  studied. 

The  number  of  the  important  fruit  variations  borne  by 
individual  citrus  trees  differed  greatly.  A  few  trees  in  all 
of  the  varieties  have  been  found  without  any  apparent  or 
marked  variation  in  fruits  other  than  the  usual  modifica- 
tions of  size,  shape,  texture  of  rind,  color,  and  quality  which 
are  probably  due  to  the  influence  of  season,  culture,  or  other 


Cooperative  Improvement  of  Citi^us  Varieties.      253 

environmental  conditions.  Fortunately,  from  the  stand- 
point of  the  conservation  and  improvement  of  the  varieties, 
the  inherent  variations  have  been  found  to  occur  most  fre- 
quently in  the  trees  of  the  inferior  strains  of  all  of  the  varie- 
ties. The  most  productive  trees  in  all  cases  so  far  studied 
and  those  bearing  the  most  desirable  fruits  have  produced 
comparatively  few  of  these  marked  fruit  or  other  bud  varia- 
tions.1 


Dry  Strain  of  the  Washington  Navel  Orange. 

FIG.  2. — Typical  fruits  from  a  tree  of  the  dry  strain  of  the  Washington  Navel 
orange  variety,'  showing  the  undesirable  and  worthless  characteristics  of  the 
fruits  of  this  strain.  This  and  other  inferior  strains  originated  as  bud  varia- 
tions of  the  best  strain,  and  their  accidental  propagation  has  been  the  source 
of  great  loss  annually  to  the  growers  possessing  them. 

ORIGIN  OF  STRAINS. 

The  term  "  strain  "  is  here  used  to  designate  a  group  of 
individuals  of  a  horticultural  variety  which  differ  from  all 
other  individuals  of  the  variety  in  one  or  more  constant  and 
recognizable  characteristics  capable  of  perpetuation  through 
vegetative  propagation. 

1  The  detailed  results  of  the  investigation  of  the  variations  of  citrus  varie- 
ties in  California  have  been  presented  in  a  series  of  publications  of  the  United 
States  Department  of  Agriculture.  These  reports  are  in  Department  Bulletins 
623,  624,  and  697,  to  which  the  reader  is  referred  for  further  information  as  to 
the  occurrence  and  frequency  of  bud  variations. 


«ON  OF  SUBTROPICAL  HORTICULIUKt 
COLLEGE  OF  AGRICULTURE 
BERKELEY.  CALIFORNIA 


254       Yearbook  of  the  Department  of  Agriculture,  1919. 

One  of  the  first  and  most  important  individual  fruit  va- 
riations observed  in  Washington  Navel  orange  trees  was  a 
large,  coarse  fruit,  which  is  commonly  called  an  Australian 
Navel  orange.  Soon  after  the  discovery  of  this  single  fruit 
variation  in  the  crop  of  a  typical  Washington  Navel  tree,  a 
limb  was  found  in  a  near-by  Washington  Navel  tree  bearing 
56  typical  Australian  fruits.  A  further  study  of  this 


Several  Strains  of  Lemons  from  the  Same  Tree. 

FIG.  3. — Typical  fruits  of  several  strains  produced  by  different  branches  on  a  variable 
Lisbon  lemon  tree  which  was  grown  from  a  single  bud. 

orchard  revealed  several  trees  bearing  all,  or  nearly  all, 
Australian  fruits,  and  having  the  peculiar  upright  habit  of 
growth  so  characteristic  of  the  trees  of  this  strain. 

An  investigation  of  the  single  fruit  variations  found  in 
the  trees  of  the  varieties  studied  revealed  their  occurrence  in 
other  trees  as  limb  sports  and  in  other  cases  as  individual 
trees.  This  condition  illustrates  the  probable  origin  of  the 


Cooperative  Improvement  of  Citnis  Varieties.      255 

many  diverse  strains  in  citrus  varieties,  due  to  the  accidental 
propagation  of  limb  sports,  and  is  an  important  reason  for 
obtaining  performance  records  for  use  in  the  selection  of 
bud  wood  for  propagation. 

So  far,  13  strains  of  the  Washington  Navel  orange,  12 
strains  of  the  Valencia  orange,  6  strains  of  the  Marsh 
grapefruit,  8  strains  of  the  Eureka  lemon,  and  5  strains 


A  Drone  Tree. 

FIG.  4. — A  typical  unproductive  or  drone  tree  of  the  shade-tree  strain  of  the 
Eureka  lemon  variety.  The  trees  of  this  strain  show  extraordinarily  rank 
vegetative  growth  and  bear  light,  inferior  crops  as  compared  with  the  trees  of 
the  productive  strain. 

of  the  Lisbon  lemon  varieties  have  been  found,  their  char- 
acterictics  described,  and  the  behavior  of  typical  trees  de- 
termined. The  origin  of  all  these  strains  has  been  traced 
to  bud  variations,  examples  of  \vhich  are  shown  in  figure  3. 
Their  distribution  in  established  orchards  has  been  largety 
the  result  of  accidental  propagation  of  the  bud  variations, 
due  to  a  lack  of  knowledge  of  the  importance  of  the  varia- 


256       Yearbook  of  the  Department  of  Agriculture,  1919. 

tions  and  their  significance  in  the  work  of  maintaining  the 
citrus  varieties. 

The  extent  of  the  occurrence  of  trees  of  the  diverse  strains  of 
the  citrus  varieties  in  California  has  been  studied  carefully 


A  Productive  Lemon  Tree. 

FIG.   5. — A  typical  productive  tree  of  the  best  strain  of  the  Eureka  lemon 
variety. 

in  many  districts  by  means  of  orchard  surveys.  The  per- 
centage of  off  type  trees,  that  is,  trees  belonging  to  strains 
different  from  those  desired  in  the  orchards  and  usually 
inferior  to  them,  has  been  found  to  vary  from  10  to  approxi- 
mately 90.  An  average  of  25  per  cent  of  the  trees  in  the 


Cooperative  Improvement  of  Citrus  Varieties.      257 

orchards  studied  have  been  found  to  belong  to  strains  which 
differ  markedly  from  the  typical  or  best  strain  of  the 
variety.  The  largest  percentage  of  variations 
from  the  superior  strains  has  been  found  in  the 
younger  orchards. 

The  trees  of  one  of  the  strains  of 
the  Eureka  lemon  variety  possess 
unusual  vigor  of  growth  and  habit- 
ually bear  light  crops  of  infe- 
rior fruits.     A  typical  tree  of 
this  strain  is  shown  in  figure  4. 
On   account   of  their  large 
size   as  compared   with   the 
trees  of  the  productive 
strain,    the    density    of 
their    foliage,    and 
their    poor    crops, 
they    have    been 
called  shade  trees. 
These  trees  usu- 
ally  develop   a 

very  large  number  of  rank,  up- 
right-g  rowing,  nonfruiting 
branches,  commonly  called 
suckers.  Formerly  this  sucker 
growth  was  generally  used  by 
citrus  nurserymen  for  propa- 
gation. In  one  of  the  older 
Eureka  lemon  orchards  in 
southern  California  10  per  cent 
of  the  trees  were  found  to  be 
of  the  Shade-Tree  strain.  In 
a  younger  orchard,  the  trees  of 
which  had  been  grown  from 
sucker  buds  secured  in  the 
older  grove,  25  per  cent  of  the 
trees  were  found  to  be  of  this 
strain.  In  a  still  younger  orchard,  where  the  trees  had  been 
grown  from  sucker  buds  secured  in  the  second  orchard,  the 
percentage  of  shade  trees  was  found  to  be  75.  This  astonish- 
ing increase  in  the  percentage  of  shade  trees  in  the  younger 


Orange  Variations  on  the 
Same  Branch. 

FIG.  6. — A  branch  from  a  Ruby 
blood-orange  tree  bearing  a  fruit 
possessing  a  navel  'and  a  normal 
fruit  without  a  navel ;  an  example 
of  the  variation  of  fruits  frequently 
found  in  citrus  trees. 


258       Yearbook  of  the  Department  of  Agriculture,  1919. 


orchards  is  due  to  the  fact  that  the  bud  cutters  in  each  in- 
stance secured  a  large  share  of  their  bud  wood  from  the 
trees  of  the  Shade-Tree  strain,  as  the  sucker 
growth  was  most  easily  secured  from  them. 

The  shade  trees  in  these  three  orchards  have 
recently    been    top-worked,    using    fruit-bearing 
bud  wood  secured  from  superior  trees  of  the  Pro- 
ductive strain  of  the  Eureka  variety, 
an    example    of    which   is   shown    in 


figure  5.    Without  ex- 
ception    the     growth 
and  fruits  from  these 
selected  buds,  which  were  top- 
work  e  d   on   the    shade-tree 
trunks,  as  shown  in  figure  7, 
have  proved  to  be  of  the  de- 
sired   Productive    strain,    as 
shown  in  figure   8.     Many 
other  equally  striking  and  im- 
portant instances  of  the 
development    and   subse- 
quent elimination  of  un- 
desirable strains  in  Cali- 
fornia    citrus     orchards 
might  be  described.     In 
every   case    investigated, 
the  origin  of  these  strains 
has  been  traced  to  bud 
variations,  an  example  of 
which  is  shown  in  figure 
6,  which  are  of  frequent 
occurrence   and   of   very 
great    importance    from 
the  viewpoint  of  the  con- 
servation   and    improve- 
ment  of  the   established 
citrus  varieties. 


A  Top- Worked  Shade  Tree. 
FIG.  7. — A  typical  Eureka  lemon  shade 
tree,  such  as  that  shown  in  figure  4,  top- 
worked  with  buds  secured  from  a  superior 
performance-record  parent  tree,  such  as 
that  shown  in  figure  5.  This  photograph 
was  taken  three  months  after  top-working. 


Cooperative  Improvement  of  Citrus  Varieties.      259 
ISOLATION  OF  THE  STRAINS. 

Enough  evidence  has  been  secured  to  warrant  the  asser- 
tion that  all  the  strains  of  each  of  the  citrus  varieties  dis- 
covered in  these  investigations  can  be  isolated  through  bud 


Good  Results  from  Top- Working. 

FIG.  8. — A  top-worked  shade  tree  of  the  Eureka  lemon  variety,  such  as  that 
shown  in  figure  1,  three  years  after  top-working.  The  barren,  rank  growth  of 
the  original  shade  tree  has  been  replaced  with  the  productive  normal  growth 
of  the  best  strain.  Out  of  16,000  trees  in  this  orchard  3,200  worthless  shade 
trees  have  been  successfully  top-worked. 

selection.  This  conclusion  is  not  intended  to  convey  the 
idea  that  bud  variation  within  these  strains  can  be  entirely 
eliminated;  on  the  contrary,  the  investigations  have  shown 
that  some  variation  will  likely  continue  as  long  as  the 
strains  are  propagated. 

ftiSiGN  OF  SUBTROPICAL  HORTICULTURE 

COLLEGE  OF  AGRICULTURE 

BERKELEY,  CALIFORNIA 


260       Yearbook  of  the  Department  of  Agriculture,  1919. 

What  has  been  demonstrated  is  that  variation  can  be  con- 
trolled by  bud  selection  to  such  an  extent  that  the  indi- 
viduals of  the  strain  can  be  brought  to  a  condition  of  prac- 
tical uniformity  as  regards  crop  production  and  other  char- 
acteristics. At  this  time  there  are  several  thousand  acres  of 
bearing  citrus  orchards  in  California  in  which  the  trees 
have  been  propagated  from  carefully  selected  buds,  secured 
from  superior  performance-record  trees.  In  these  orchards 
the  progenies  of  each  of  the  parent  trees  have  been  kept  sep- 
arate. Performance-record  studies  of  these  progenies  and  a 
comparison  of  their  behavior  with  that  of  the  parent  trees 
conclusively  demonstrate  that  through  bud  selection  each  of 
the  important  citrus  strains  has  been  isolated.  The  uni- 
formity of  the  progenies  and  the  superior  and  heavy  crops 
of  those  of  desirable  strains  have  proved  beyond  any  doubt 
that  it  is  practicable  commercially  to  isolate  and  propagate 
only  the  best  strains  and  to  eliminate  the  inferior  ones 
through  careful  bud  selection,  l>ased  upon  individual-tree 
records  and  intimate  tree  knowledge. 

COMPARATIVE  VALUE  OF  THE  STRAINS. 

As  a  rule,  only  one  of  the  many  strains  in  each  of  the 
citrus  varieties  has  been  found  to  be  worthy  of  commercial 
propagation  and  profitable  for  cultivation.  The  value  of  the 
product  of  the  trees  of  the  best  strains  as  compared  with 
that  of  the  trees  of  the  inferior  strains  may  be  illustrated  by 
the  records  of  production  of  the  trees  of  the  best  Washing- 
ton Navel  orange  strain  and  those  of  the  inferior  Australian 
strain  in  the  investigational  performance-record  plat.  In 
these  studies  it  was  found  that  the  trees  of  the  best  Washing- 
ton Navel  strain  produced  an  average  of  4.73  packed  boxes 
of  oranges  per  tree  per  year  during  the  period  of  observa- 
tion. Under  similar  conditions  the  trees  of  the  Australian 
strain  produced  0.76  of  a  packed  box  per  tree  per  year. 
On  an  acre  basis,  this  yield  amounted  to  378.6  packed 
boxes  per  acre  for  the  best  trees,  compared  with  61  packed 
boxes  per  acre  for  the  inferior  trees.  The  actual  value  of 
this  production  was  $635.05  per  acre  annually  for  the  high- 
producing  trees,  as  compared  with  $100.0-4  for  the  low- 
producing  trees  of  the  undesirable  strain.  Even  greater 


Cooperative  Improvement  of  Citrus  Varieties.     261 

differences  in  production  and  value  of  the  crops  from  the 
trees  of  different  strains  have  been  found  in  other  varieties. 
When  it  is  remembered  that  on  the  average  25  per  cent  of 
the  trees  in  the  orchards  studied  have  been  found  to  be  in- 
ferior strains,  the  commercial  importance  of  growing  only 
trees  of  the  best  strains  can  be  appreciated. 

OBJECT  OF  COMMERCIAL  TREE-RECORD  WORK. 

The  trees  of  the  best  strain  in  e#ch  variety  have  usually 
been  found  to  be  the  heaviest  producers  of  fruit.  On  the 
other  hand,  the  trees  of  the  inferior  strains  have  usually  been 
found  to  bear  light  crops  of  inferior  commercial  quality. 
For  this  reason  individual-tree  records  of  production  are  of 
very  great  value  in  ^determining  the  proportion  of  different 
strains  of  trees  in  citrus  orchards. 

The  demonstration  of  this  condition  in  both  experimental 
and  commercial  tree- record  work  has  led  many  of  the  lead- 
ing citrus  growers  to  undertake  individual-tree  record  work 
in  their  orchards.  Such  records  are  now  being  kept  on  more 
than  50,000  acres  of  citrus  orchards  in  California. 

The  object  of  the  commercial  tree  records  is  (1)  to  locate 
the  drone  trees,  or  those  of  the  inferior  strains  in  the  or- 
chards; (2)  to  find  the  superior  trees,  or  those  from  which 
bud  wood  may  be  secured  for  propagation;  (3)  to  aid  in 
giving  the  trees  individual  care,  such  as  cutting  out  limb 
sports  or  other  undesirable  growth,  treatment  for  disease, 
or  any  tree  injury ;  and  (4)  to  secure  definite  evidence  as  to 
the  effect  of  cultural  treatments  and  other  experimental  tests. 

METHOD   OF  KEEPING  INDIVIDUAL-TREE  RECORDS. 

The  method  of  keeping  individual-tree  records  in  citrus 
orchards  now  commonly  used  in  California  will  be  briefly 
described.  Various  minor  modifications  of  this  method 
have  been  and  are  being  tried  in  some  orchards,  but  the  prin- 
ciples underlying  this  work  are  fundamentally  the  same  in 
all  cases.  It  may  be  found  advisable  to  modify  or 
change  the  method  somewhat,  owing  to  local  conditions,  but 
these  changes  should  not  be  made  until  experience  has  shown 
them  to  be  necessary  in  order  that  the  records- may  be  secured 
in  the  most  natural  and  logical  manner. 


VISION  OF  SUBTROPICAL  HORTICULTURE 
*  COLLEGE  OF  AGRICULTURE 
BERKELEY,  CALIFORNIA 


262      Yearbook  of  the  Department  of  Agriculture,  1919. 


INDIVIDUAL-TREE    NUMBERS. 

Each  individual  tree  in  the  orchard  receives  a  number. 
This  number  consists  of  three  parts,  (1)  the  number  of  the 
block  or  division  of  the  orchard,  (2)  the  number  of  the  row 
in  the  block,  and  (3)  the  position  of  the  tree  in  the  row. 
always  counting  from  some  fixed  point,  as,  for  example,  the 

irrigation  head.  A  tree  lo- 
cated in  block  14,  row  18,  and 
the  twentieth  tree  in  the  row, 
has  the  number  14-18-20. 
Where  there  are  several  dif- 
ferent orchards  the  tree 
number  in  the  performance- 
record  notes  is  preceded  by 
the  number  or  name  of  the 
orchard  or  its  abbreviation. 

In  the  case  of  bearing 
trees  this  number  is  painted 
on  the  tree  trunk  or  on  one 
of  the  main  limbs,  arrang- 
ing the  number  in  a  vertical 
column  in  the  form  shown  in 
figure  9.  The  figures  are 
made  with  a  common  letter- 
ing brush  and  pure  white-lead 
paint.  Very  young  trees,  on 
which  space  is  not  available 
for  painting  the  number,  are 
designated  by  attaching  a 
metal  or  other  tag  bearing  the  number. 

The  tree  numbers  are  always  placed  in  the  same  relative 
position  on  all  the  trees  in  the  orchard,  for  convenience  in 
finding  them.  Large,  distinct  figures  are  made,  so  that  they 
are  easily  legible.  The  cost  of  tree  numbering  has  varied 
somewhat  with  labor  conditions,  but  at  present  the  numbers 
are  being  applied  at  an  average  cost  of  about  2  cents  a  tree. 

PICKING. 

When  picking  the  trees  where  individual-tree  records  are 
secured  it  is  usually  necessary  to  distribute  the  field  boxes 
to  the  individual  trees  instead  of  in  box  BOWS,  as  is  ordi- 


Individual-Tree   Numbering. 

FIG.  9. — The  arrangement  of  an  in- 
dividual-tree number  on  the  trunk  of 
a  bearing  citrus  tree  in  a  commer- 
cial orchard. 


Cooperative  Improvement  of  Citrus  Varieties.      263 

narily  done.  Each  picker  gathers  the  fruit  from  one  tree, 
and  usually  the  same  man  picks  all  the  trees  in  each  row. 
All  the  fruit  from  each  tree  is  placed  in  boxes  at  its  base, 
as  shown  in  figure  10.  Care  is  taken  in  the  beginning  to 


Commercial  Performance  Record  Taking. 

FIG.  10. — Securing  performance  record  of  the  number  of  full  boxes  and  the 
weight  of  a  partly  filled  box  of  fruit  produced  by  a  Washington  Navel  orange 
tree  in  a  commercial  orchard. 

see  that  none  of  the  fruit  from  a  tree  is  accidentally  carried 
in  the  picking  sack  to  a  neighboring  tree.  Pickers  quickly 
realize  the  importance  of  keeping  the  fruit  of  each  tree  sep- 
arate. In  some  instances  this  arrangement  has  been  found 
to  stimulate  care  in  picking  and  to  accelerate  markedly  the 
rate  of  picking.  Each  picker's  work  is  always  open  to 
inspection.  With  one  picker  on  a  row  the  natural  tendency 


264      Yearbook  of  the  Department  of  Agriculture,  1919. 

is  to  induce  the  slower  pickers  to  keep  up  with  the  faster 
workers.  Inasmuch  as  the  field  boxes  are  near  the  tree  being 
picked,  this  arrangement  does  away  with  the  necessity  for 
each  man  walking  with  his  filled  picking  sack  from  the  tree 
to  the  box  row,  as  was  formerly  the  case,  and  in  this  way 
saves  considerable  time.  Extensive  experience  with  com- 
mercial individual-tree  picking  work  during  the  past  eight 


Weighing,  an  Essential  Step. 

FIG.  11. — Recording  the  weight  of  lemons  produced  by  a  Eureka  tree  at  the 
time  of  one  of  the  regular  monthly  pickings.  The  arrangement  of  truck  and 
scales  is  convenient  for  securing  the  weight  of  fruit  where  this  method  of  keep- 
ing individual-tree  records  is  desired. 

years  .has  shown  that  the  cost  of  picking  the  crops  in  this 
way  is  not  much,  if  any,  greater  than  where  the  crops 
are  picked  in  the  ordinary  manner. 

RECORDING  INDIVIDUAL-TREE  PERFORMANCE. 

The  foreman  of  the  picking  crew  usually  records  the 
individual-tree  yields,  as  shown  in  figure  11.  Each  day, 
after  the  trees  have  been  picked  and  before  the  boxes  of 
fruit  are  assembled  for  transporting  to  the  packing  house, 


Cooperative  Improvement  of  Citi^us  Varieties.      265 

or  at  convenient  times  during  the  day,  the  foreman  records 
in  a  field  notebook  the  number  of  boxes  picked  from  each 
tree.  The  partly  filled  boxes  are  usually  recorded  as  esti- 
mated fractional  parts  of  a  full  box,  frequently  as  eighths. 
Some  growers  do  not  consider  this  estimate  accurate  enough 
and  weigh  each  partly  filled  box  and  record  its  weight  of 
fruits  in  terms  of  pounds  and  ounces. 

A  convenient  and  widely  used  form  for  recording  the 
yield  of  each  individual  tree  is  as  follows : 

Variety Date 


Tree  No. 

Boxes. 

Part  boxes. 

Quality. 

Notes. 

j 

2  

3 

- 

If  more  than  one  picking  is  made  from  each  tree,  enough 
additional  columns  are  provided  to  care  for  these  data. 

Where  this  form  is  used  it  is  only  necessary  for  the  fore- 
man to  insert  the  name  of  the  variety,  the  date  of  picking, 
and  the  block  and  row  number  on  each  page.  Care  is  taken 
to  look  at  the  tree  number  each  time  before  recording  the 
data,  in  order  to  be  sure  that  no  mistake  is  made. 

In  addition  to  the  number  of  boxes  of  fruit  borne  by 
each  tree  the  foreman  usually  makes  a  note  of  the  apparent 
quality  of  the  fruits  and  of  any  unusual  tree  condition. 
These  notes  are  usually  made  by  means  of  symbols,  as,  for 
example,  A,  for  first  grade;  B,  for  second  grade;  and  C, 
for  culls.  A  tree  showing  evidences  of  disease  is  marked  by 
recording  X  along  with  the  yield  data.  Various  amplifi- 
cations of  this  system  are  in  use  in  many  orchards,  and  have 
been  found  to  be  of  great  service  in  giving  the  trees  individ- 
ual attention  and  care. 

COOPERATION  IN  SECURING  AND  DISTRIBUTING  BUD 
WOOD. 

The  California  Fruit  Growers'  Exchange,  a  cooperative 
organization  of  about  10,000  members,  recognizing  the  com- 


266      Yearbook  of  the  Department  of  Agriculture,  1919. 

mercial  importance  of  this  work,  established  in  May,  1917, 
a  department  of  bud  selection.  The  work  of  this  depart- 
ment is  to  secure  bud  wood  from  superior  performance- 
record  trees  and  distribute  it  to  propagators.  The  head  of 
this  department  is  a  scientifically  trained  man,  who  is 
familiar  with  the  research  which  has  led  up  to  the  intro- 
duction of  improved  methods  of  securing  and  propagating 
reliable  citrus  bud  wood.  The  object  of  the  work  is  to  put 
into  practice  the  results  of  the  investigation  of  this  subject 
by  the  Bureau  of  Plant  Industry  in  order  to  improve  the 
quantity  and  quality  of  the  citrus  production  in  the  State 
as  a  whole.  It  is  looked  upon  by  those  interested  as  a 
public  service,  both  to  the  producer  and  to  the  consumer, 
and  for  this  reason  has  the  whole-hearted  cooperation  and 
support  of  everyone  concerned.  This  service  is  performed 
at  cost,  and  from  the  beginning  has  been  self-supporting. 
The  operation  of  this  department  is  briefly  outlined  in  the 
following  paragraphs. 

THE  SELECTION  OF  SUPERIOR  PARENT  TREES. 

For  several  years  preceding  the  establishment  of  the  bud- 
selection  department  many  of  the  leading  citrus  growers 
possessing  the  best  orchards  in  the  State  had  been  keeping 
individual-tree  records  of  all  the  trees  in  their  orchards. 
Some  of  the  largest  orchards  are  approximately  1,500  acres 
in  extent.  The  tree  records  of  all  of  these  orchards  were 
made  available  for  the  work  of  securing  and  distributing 
reliable  bud  wood.  A  careful  survey  was  made  of  these 
orchards,  which  are  located  in  every  important  citrus  dis- 
trict in  California,  and  a  detailed  analysis  was  made  of  the 
individual-tree  records  of  production.  The  orchards  show- 
•ing  the  best  and  most  consistent  records  for  each  variety  and 
those  where  the  fruit  was  found  to  bring  the  highest  market 
price  in  its  class  were  selected  for  more  detailed  study.  Usu- 
ally three  or  more  years  of  individual-record  keeping  were 
required  before  any  selection  of  parent  trees  was  made. 

In  the  orchards  where  the  conditions  were  found  to  be 
satisfactory  for  this  work  all  the  highest  yielding  trees  were 
carefully  inspected  in  connection  with  their  past  perform- 
ance. The  type  of  fruit  was  carefully  examined.  The  uni- 


Cooperative  Improvement  of  Citrus  Varieties.      267 


formity  of  fruits  on  all  parts  of  the  trees  was  studied.  All 
trees  bearing  irregular  fruits  or  those  having  variable 
branches  were  immediately  excluded  from  further  considera- 
tion. The  highest  yielding  trees  which  were  found  to  bear 
uniform  fruits  of  the  best 
type  for  the  variety  were 
selected  as  sources  of 
bud  wood  for  propaga- 
tion. In  this  work  the 
individual-tree  records 
have  been  found  to  be 
invaluable.  Experience 
has  shown  that  an  in- 
telligent selection  of 
trees  could  not  have  been 
made  without  them.  In 
addition  to  the  records 
and  the  examination  of 
the  trees,  their  habit  of 
growth,  and  the  charac- 
teristics of  the  foliage 
and  fruits,  the  selection 
of  parent  trees  has  been 
guided  by  an  intimate 
knowledge  of  the  trees 
of  the  variety  gained 
through  systematic  indi- 
vidual-tree record  work 
by  those  having  a  nat- 
ural inclination  for  it. 


KIND   OF   BUD   WOOD. 


Fruit-Bearing  Orange  Bud  Wood. 

FIG.  12. — Typical  fruit-bearing  Valencia 
orange  bud  stick,  showing  the  type  of 
bud  wood  secured  for  propagation. 


Only  fruit-bearing  bud 
wood  is  cut  from  the 
parent  trees  for  propa- 
gation. Usually  only  those  bud  sticks  are  secured  which 
have  one  or  more  typical  fruits  attached,  as  shown  in 
figure  12.  As  a  rule,  5  large  viable  buds  are  obtained 
on  each  orange  bud  stick  and  10  strong  buds  with  each 
lemon  bud  stick.  The  buds  from  this  young  and  somewhat 


268      Yearbook  of  the  Department  of  Agriculture,  1919. 

immature  growth  have  been  found,  both  experimentally 
and  commercially,  to  give  better  results  in  propagation  than 
the  buds  from  older  growth  or  from  sucker  wood.  On  the 
average,  500  good  buds  are  secured  from  each  full-bearing 
parent  tree  during  a  season. 

HANDLING   THE   BUD   WOOD. 

The  bud  sticks  from  each  parent  tree  are  kept  in  separate 
bundles.  A  tag  with  a  serial  number  is  attached  to  each 
bundle.  A  duplicate  tag  with  the  same  serial  number,  the 
number  of  the  tree  from  which  the  buds  were  cut,  and  the 
name  of  the  propagator  to  whom  the  buds  are  to  be  sent  is 
filed  in  the  bud-selection  department.  With  this  informa- 
tion, together  with  the  individual-tree  records,  it  is  possible 
at  any  time  to  trace  any  progeny  in  a  nursery  to  the  parent 
tree  and  to  examine  the  performance  record  of  the  parent 
tree  for  the  information  of  the  nurseryman,  a  prospective 
purchaser  of  the  progeny  trees,  or  any  other  interested 
person. 

The  leaves  of  each  bud  stick  are  trimmed  off  immediately 
after  cutting,  as  shown  in  figure  13.  As  soon  as  all  the  bud 
sticks  desired  are  secured  from  a  tree,  they  are  tied  in  a 
bundle,  tagged,  and  packed  in  moist,  sterile  sphagnum  moss. 
Several  bundles  of  bud  wood  are  usually  packed  tightly 
together,  and  this  package  is  covered  with  strong  burlap. 
These  packages  are  kept  in  a  cool  temperature,  preferably 
about  70°  F.,  until  the  bud  wood  is  delivered  to  the  prop- 
agator. Under  these  conditions  citrus  bud  wood  can  be 
kept  safely  for  several  weeks.  However,  experience  has 
shown  that  it  is  desirable  to  use  the  buds  as  soon  as  possi- 
ble after  cutting  them  from  the  parent  trees. 

COST   OF    THE    WOOD. 

Inasmuch  as  the  business  of  securing  and  distributing 
these  bud§  is  conducted  by  a  cooperative  nonprofit  organi- 
zation, the  buds  are  supplied  to  propagators  at  cost.  At 
the  present  time  a  charge  of  5  cents  is  made  for  each  good 
bud  to  members  of  the  cooperative  organization  or  6  cents 
for  each  bud  to  propagators  who  are  not  members  of  the 
organization.  As  soon  as  the  volume  of  business  warrants, 


Cooperative  Improvement  of  Citrus  T  arieties.      269 

this  cost  will  be  reduced.  The  owners  of  the  trees  from 
which  the  buds  are  cut  are  paid  1|  cents  for  each  bud  secured 
from  their  trees. 


Fruit-Bearing  Lemon  Bud  Wood. 

FIG.  13. — Two  typical  bud  sticks  on  a  superior  Eureka  lemon  parent  tree. 
The  leaves  have  been  cut  off  the  one  on  the  right  in  order  to  show  the 
method  of  preparing  the  bud  sticks  for  packing. 

The  cost  of  maintaining  this  bud-selection  department 
includes  the  pa37ment  for  the  buds  to  the  owners  of  the 
parent  trees,  the  assembling,  tabulating,  and  studying  of 
extensive  individual-tree  data,  the  selection  of  the  superior 


270       Yearbook  of  the  Department  of  Agriculture,  1919. 

parent  trees,  collecting  information  regularly  as  to  the  be- 
havior of  the  buds  and  the  trees  grown  from  them,  and  the 
survey  of  new  orchard  areas  for  the  location  of  additional 
parent  trees.  In  1919  an  experimental  citrus  nursery  of  7 
acres  was  established  for  the  purpose  of  trying  out  different 
methods  of  budding,  determining  the  comparative  value  of 
different  kinds  of  stocks,  and  securing  other  important 
information  for  the  benefit  of  the  propagators  and  the 
growers. 

USES  OF  SELECTED   BUDS. 

The  buds  secured  from  the  superior  parent  trees  are  be- 
ing extensively  used  by  growers  for  top-working  undesirable 
or  drone  trees  in  established  orchards  or  for  top-working 
the  trees  of  one  citrus  variety  with  another  and  by  propa- 
gators who  are  growing  trees  for  sale  or  for  their  own  plant- 
ing. Up  to  this  time  a  large  proportion  of  the  buds  have 
been  sold  to  nurserymen,  who  quickly  realized  the  impor- 
tance of  furnishing  to  planters  trees  grown  from  reliable 
buds.  An  illustration  of  nursery  trees  grown  from  these 
buds  is  shown  in  figure  14.  In  fact,  under  present  conditions 
it  is  almost  impossible  for  nurserymen  in  California  to  sell  at 
any  price  any  other  kind  of  citrus  trees.  The  trees  grown 
from  the  selected  buds  sell  for  a  much  greater  price  than 
the  added  cost  of  the  buds  to  the  nurserymen.  The  increas- 
ing appreciation  by  citrus  growers  of  the  importance  of 
planting  good  trees  makes  it  seem  certain  that  the  utiliza- 
tion of  this  work  will  be  greatly  increased  in  the  near  future. 

In  the  following  table  the  development  of  the  bud-selec- 
tion service  is  shown  by  the  number  of  buds  sold  each  season 
from  the  inauguration  of  this  work  to  date : 

Buds  sold  from  superior  parent  trees. 


Year  and  budding  season. 

Number 
of  buds 
sold. 

Year  and  budding  season. 

Number 
of  buds 
sold. 

Season  of  1917: 
Spring  

25  550 

Season  of  1919: 

Fall  

82  850 

Fall 

Season  of  1918: 

Total  

Fall  

SS  958 

Cooperative  Improvement  of  Citrus  Varieties.      271 

Out  of  the  total  number  of  buds  distributed  approxi- 
mately 75,000  were  used  for  top-working  established  unde- 
sirable trees,  and  the  remainder  were  used  by  propagators  for 
propagating  nursery  trees.  These  buds  were  secured  from 
superior  parent  trees  in  21  orchards  located  in  southern  Cali- 
fornia. 

During  the  war  comparatively  little  citrus  propagation 
was  carried  on.  Since  the  close  of  the  war  California 
nurserymen  have  planted  more  than  100  bushels  of  citrus 
seed  for  growing  stocks.  This  recent  great  activity  in  stock 
production  indicates  that  there  will  be  a  very  largely  in- 
creased demand  for  the  selected  buds  for  use  in  budding  this 
stock  in  the  near  future. 

SECURING   RELIABLE  TREES. 

The  bud-selection  department  maintains  an  office  where 
records  are  kept  of  all  the  available  trees  for  sale  that  were 
grown  from  the  selected  buds  furnished  by  that  department. 
The  parentage  of  these  trees,  their  condition  of  growth,  and 
other  details  are  furnished  to  all  inquirers  without  cost. 
From  these  data  the  planters  can  intelligently  decide  where 
to  buy  reliable  and  satisfactory  trees.  This  service  is  prov- 
ing to  be  an  invaluable  aid  to  citrus  growers. 

The  widespread  membership  of  the  cooperative  organiza- 
tion, continually  advised  as  to  the  progress  of  the  work  of 
bud  selection  arid  propagation,  has  been  the  most  effective 
way  through  which  this  information  has  been  made  avail- 
able to  the  citrus  industry  as  a  whole.  The  officials  of  the 
State  University  and  the  United  States  Department  of  Ag- 
riculture, farm  journals,  and  horticultural  clubs  have  co- 
operated in  bringing  this  work  to  the  attention  of  all  inter- 
ested persons.  At  present  there  seems  to  be  no  good  reason 
why  every  prospective  planter  in  California  should  not  be 
able  to  secure  reliable  information  as  to  sources  of  good 
citrus  trees  for  planting. 

RESULTS  OF  BUD  SELECTION. 

Extensive  orchards  of  all  the  important  commercial  varie- 
ties, in  which  the  trees  were  propagated  from  carefully 
selected  buds  secured  from  superior  performance-record 


272       Year-look  of  the  Department  of  Agriculture,  1919. 

trees,  are  now  in  bearing  in  California.  Careful  surveys  of 
these  orchards  have  shown  without  any  doubt  that  they  are 
superior  to  comparative  orchards  in  which  the  trees  were 


Strain  Characteristics  Revealed  in  the  Nursery  Trees. 
FIG.  14. — Nursery  trees  of  the  best  strain  of  the  Eureka  lemon  variety  two 
years  after  budding  on  sour-orange  stock.  These  young  trees  blossomed  and 
small  fruits  developed  while  still  in  the  nursery  row.  This  is  characteristic  of 
the  young  trees  propagated  by  the  use  of  the  improved  methods  described  in 
this  article. 

propagated  without  care  in  bud  selection.  It  is  becoming 
increasingly  difficult  to  find  }Toung  citrus  orchards  where 
the  trees  were  propagated  without  the  use  of  carefully  se- 
lected buds.  This  demonstration  of  the  superiority  of  the 


DIVISION  OF  SUBTROPICAL  HOW1CWJW:  t 

COLLEGE  OF  AGRICULTURE 

BERKELEY,  CALIFORNIA 


Trees  Produced  from  Selected  Buds. 

FIG.  15a. — A  typical  3-year-old  Eureka  lemon  tree  in  a  large  com- 
mercial orchard,  showing  the  early  production  of  uniformly  good  fruits 
secured  from  trees  propagated  from  fruit-bearing  wood  buds  selected  from 
superior  performance-record  parent  trees. 

FIG.  151). — A  3-year-old  Marsh  grapefruit  tree  in  a  commercial  orchard, 
showing  the  heavy  production  of  uniformly  desirable  fruits  developed  by 
trees  propagated  from  selected  buds  secured  from  superior  performance- 
record  parent  trees. 


$$**' 


Cooperative  Improvement  of  Citrus  Varieties.      275 

trees  grown  from  buds  secured  in  the  manner  described  in 
this  article  has  been  the  compelling  force  that  has  made  the 
bud-selection  work  commercially  successful. 

The  trees  grown  from  the  selected  buds  have  shown  un- 
usually early  production  of  heavy  crops,  as  shown  in  figure 
156,  and  are  bearing  regular  crops  of  uniformly  superior 
quality;  in  other  words,  they  are  producing  fruits  similar 
to  those  borne  by  the  parent  trees.  This  uniformly  good 
production,  an  example  of  which  is  shown  in  figure  15a,  has 
been  achieved  at  no  greater  cost  than  the  irregular  crops 
having  a  considerable  proportion  of  fruits  of  worthless 
strains,  produced  by  mixed-strain  trees,  in  the  ordinary 
orchard.  The  uniform  fruits  on  the  trees  grown  from  the 
selected  buds  reduce  the  cost  of  assorting  and  packing  the 
crops,  compared  with  the  ordinary  crops.  The  uniform 
market  grades  made  possible  by  the  uniformity  of  fruits 
increase  the  confidence  of  the  consumer  in  the  fruit  and 
induce  a  larger  consumption.  This  condition  is  econom- 
ically valuable,  both  to  the  producer  and  to  the  consumer; 
it  stabilizes  the  industry  as  a  whole  and  adds  materially  to 
the  reputation  and  value  of  the  crops. 

COOPERATION  AN  ESSENTIAL. 

The  utilization  of  the  results  of  scientific  research  in  the 
improvement  of  citrus  fruits  through  bud  selection  has 
largely  been  made  possible  through  an  organized  citrus  in- 
dustry. "While  the  investigation  of  this  subject  could  proba- 
bly have  been  carried  on"  without  this  organization,  it  was 
as  a  matter  of  fact  largely  encouraged  and  fostered  by  it. 
In  the  opinion  of  the  writer  the  widespread  use  of  the  im- 
proved methods  of  bud  selection  and  propagation  could  not 
have  been  so  quickly  and  efficiently  introduced  commer- 
cially in  the  citrus  industry  without  the  active  participa- 
tion of  the  cooperative  growers'  organization,  the  California 
Fruit  Growers'  Exchange. 


O 


210105 


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